In the prior art it has previously been proposed to provide power supply circuits which enable a first alternating voltage of high value to be produced for the purpose of starting the discharge lamp. Then, once the lamp has fired (i.e. once it has been lit), the power supply system generates an alternating voltage of low value.
In particular, such a power supply arrangement has been proposed which is constructed around a circuit of the kind known as an H bridge. However, such an arrangement requires four interrupter for all the branches of the bridge, with the discharge lamp being connected in the central branch of the bridge. Such interrupter may carry high currents. These components are therefore expensive, because they must have low losses in the conductive state, because at a given instant, two closed interrupter are in series with the load.
When these systems are to be produced in quantity production, these prior art arrangements show certain disadvantages in view of the fact that they must have operating reliability of a high order, since vehicle lighting systems must be conducive to maximum safety.